2. Cell Cycle

3. Mitosis video from book

4. Cell Division Interphase The cytoplasmic contents double
Two centrosomes form
Chromosomes duplicate in the nucleus during the S phase

5. Cell Division Prophase
In the nucleus, chromosomes become more tightly coiled and folded.
In the cytoplasm, the mitotic spindle begins to form as microtubules rapidly grow out from the centrosomes.

6. Cell Division Prometaphase
The nuclear envelope breaks into fragments and disappears.
Microtubules extend from the centrosomes into the nuclear region.
Some spindle microtubules attach to the chromosomes.
Other microtubules meet those from the opposite poles and connect.

7. Cell Division Metaphase The mitotic spindle is fully formed.
Chromosomes align in the middle.
Centromeres of sister chromatids are facing the opposite poles of the spindle.

8. Recall - Chromatid
After DNA replication there are two identical copies called sister chromatids
Sister chromatids are connected together at the centromere

9. Cell Division Anaphase Sister chromatids separate at the centromeres.
Daughter chromosomes are moved to opposite poles of the cell (motor proteins)
Spindle microtubules not attached to chromosomes lengthen, moving the poles farther apart.
The two sides of the cell end with equal numbers of chromosomes.

10. Cell Division Telophase The cell continues to elongate.
The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei.
Chromosomes uncoil (chromatin).
The mitotic spindle disappears.

11. Cell Division
During cytokinesis, the cytoplasm is divided into separate cells.
Cytokinesis usually occurs simultaneously with telophase.

12. Cell Division Cytokinesis - Animals Cytokinesis - Plants
Cleavage furrow forms and divides cell in two
Cell plate forms and divides cell in two

13. Cell Cycle
How does the cell “know” when to move on to the next step?

14. Cell Cycle Control
How does the cell “know” when to move on to the next step?
Growth Factors (type of protein) are being produced during the G1 and G2 phases.
When they reach a high enough level, the cell knows to move on to the next phase.
This is an important area of research in biology

15. G1 checkpoint G0 G1 S Control system M G2 M checkpoint G2 checkpoint
Figure 8.8a A schematic model for the cell cycle control system G2
M checkpoint
G2 checkpoint

16. Cancer and the Cell Cycle
Cancer cells do not follow the normal signals that regulate the cell cycle
They keep dividing and can possibly spread to new areas of the organism often through the lymphatic system

17. Cancer and the Cell Cycle
Radiation is a treatment to destroy cells (kills both cancerous cells and healthy cells)
Chemotherapy is a treatment that slows/stops the growth of cells (stops good cells and bad)
Can lead to hair loss, intestinal issues, other symptoms

18. Cancer and the Cell Cycle
Fully understanding the human genome could lead to improved treatment
Certain mutations cause the cell cycle to go out of control, if we can fix those mutations perhaps we can also treat cancer more successfully

19. Recall: Chromosomes vs Chromatin
Individual chromosomes not visible, described as chromatin
Chromosomes visible
Draw these
Onion cells under light microscope

21. G0 Phase Some cells enter a phase where they will no longer divide.
These cells are still functioning (just stop the division process)
Brain neurons, heart muscle cells are a couple examples. They are still functioning and working, but they no longer enter mitosis.

22. Quiz
Put name on top of page and number 1-8

23. 1
In which phase is the chromatin beginning to condense and become visible?

24. 2
In which phase do the chromosomes meet in the middle?

25. 3
When the chromosomes are replicated and attached together they are called ‘sister ______________’.

26. 4
What is the organelle that forms the mitotic spindle (microtubules)?

27. 5
During which phase do the chromosomes duplicate, they are in the form of uncondensed chromatin, and more organelles are made?

28. 6
What are the proteins called that the DNA wraps around?

29. 7
Which phase is shown in the picture? (All three are in the same phase)

30. 8
Which phase is shown in the picture?

31. A Fern Life Cycle Gametophyte plant (n) Key Haploid (n) Diploid (2n)
Male gametangium
Spores
Sperm
Female gametangium
Egg
Mature sporophyte
Meiosis
Fertilization
Zygote
New sporophyte growing from the gametophyte
Figure Fern life cycle (step 5)

32. Diploid vs Haploid
Most cells have a two sets of chromosomes, one from the mother and one from the father
These cells are diploid cells (2n)
2n - Two sets

33. Diploid vs Haploid A haploid cell only has one set of chromosomes
1n – one set
The gametes are ‘sex cells’ and are haploid.
A male produces the sperm
A female produces the egg

34. Why? 2n 1n
2n x 2

35. A Fern Life Cycle Gametophyte plant (n) Key Haploid (n) Diploid (2n)
Male gametangium
Spores
Sperm
Female gametangium
Egg
Mature sporophyte
Meiosis
Fertilization
Zygote
New sporophyte growing from the gametophyte
Figure Fern life cycle (step 5)

36. n n Haploid gametes (n = 23) Key n Haploid stage (n) Egg cell
Figure 8.12a
Haploid gametes (n = 23)
Key n n
Haploid stage (n)
Egg cell
Diploid stage (2n) n n
Sperm cell
Meiosis
Fertilization
Ovary
Testis
Figure 8.12a The human life cycle 2n
Diploid
zygote (2n = 46)
Mitosis and
development
Multicellular diploid adults (2n = 46)

37. Chromosome 2n = 46 (2n because one from mom, one dad)
(new info)
Because most cells have one set from mom and one set from dad they are diploid
2n = 46 (2n because one from mom, one dad)
(46 total chromosomes when counting)
23 pairs of homologous chromosomes
46 individual chromosomes

38. The locus (loci) are the different positions on the chromosome where genes are located

39. Haploid vs diploid

40. Mitosis – In which cells?
Almost all cells
Somatic Cells are all the cells except the gametes (sperm/egg) or the cells that divide into the gametes (germ cells)

41. Meiosis – which cells
The germ cells undergo meiosis to form the gametes (1n - haploid)

42. Look at 138-139 – take 3 minutes to read it over and look at the images
How is this similar to Mitosis?
How is is different than Mitosis?

44. Meiosis

45. Meiosis Interphase – similar to mitosis
Chromosomes duplicate (in the uncondensed chromatin state), more organelles are formed.

46. Meiosis I
Prophase I
Homologous chromosomes, each composed of two sister chromatids, come together in pairs forming tetrads.
Chromatids of homologous chromosomes exchange segments in a process called crossing over.
(also chromatin condenses and nuclear envelope breaks down like mitosis)

47. Meiosis

48. Meiosis Metaphase I Anaphase I Tetrads align in the middle
Homologous pairs separate and move toward opposite poles of the cell.
Unlike mitosis, the sister chromatids making up each doubled chromosome remain attached.

49. Meiosis I: Metaphase I Anaphase I
Spindle microtubules attached to a centromere
Sister chromatids remain attached
Figure The stages of meiosis (part 3)
Metaphase
plate
Centromere (with a kinetochore)
Homologous chromosomes separate

50. Meiosis Telophase I Duplicated chromosomes have reached the poles.
Usually, cytokinesis occurs along with telophase.

51. Meiosis
1n (x 2) 2n
2n x 2
1n (x 2)

52. Meiosis II
The two haploid cells formed from Meiosis I enter Meiosis II

53. Meiosis Prophase II Metaphase II Anaphase II
A spindle made of microtubules forms and moves chromosomes toward the middle of the cell.
Metaphase II
Duplicated chromosomes align in the middle like they are in mitosis.
Anaphase II
Sister chromatids separate.
Individual chromosomes move toward opposite poles.

54. Meiosis II: Sister chromatids separate Telophase II and Cytokinesis
Figure
Meiosis II: Sister chromatids separate
Telophase II and Cytokinesis
Prophase II
Metaphase II
Anaphase II
Haploid daughter cells forming
Sister chromatids separate
Figure The stages of meiosis (part 6)

55. Meiosis Telophase II Chromosomes have reached the poles of the cell.
A nuclear envelope forms around each set of chromosomes.
With cytokinesis, four haploid cells are produced.
Two plant cells undergoing telophase II